<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>demo2222.........</title>
    <style type="text/css">
        *{
            margin:0;
            padding:0;
        }
        html{
            height: 100%;
            width: 100;
            font-size: 20px;
        }
        body{
            height: 100%;
            width: 100;
        }
        .page{
            height: 100%;
            overflow: auto;
        }
    </style>
</head>
<body>
    <section class="page">
        <header class="header">
            header.....
        </header>
        <section class="content">
            content....main...
        </section>
        <footer class="footer">
            <nav class="foot-nav">
                <div class="nav-item">aaaa</div>
                <div class="nav-item">bbbb</div>
                <div class="nav-item">cccc</div>
                <div class="nav-item">ddddd</div>
            </nav>
        </footer>
    </section>
</body>
</html>